TrekWeb reports that SpaceView magazine has a new interview with Patrick Stewart who talked about returning as Professor Charles Xavier in X-Men 3:

Everyone, my colleagues and I, we are all very pleased to be involved on this film. The filming would have to begin June 2005, because 20th Century Fox plans to release X-MEN 3 in July 2006. And it is not that simple to get all the cast together again. Unfortunately, Bryan Singer will not be involved this time, because he is directing the new SUPERMAN movie. And, as I said, is not certain that all the actors will be returning. But I am sure that Hugh Jackman will be back. He is such a crazy actor! I just saw him on stage in New York where he delivered such an extraordinary performance.

Stewart also addressed the rumor that Bryan Singer wants him to play Jor El in Superman:

I also heard these rumors, but so far Bryan did not ask me about it. I had recently a small heart surgery – nothing serious – and while I was at the hospital, Bryan called me. We spoke a long time – yet he did not ask me. But since I am already in two big franchises, why not also in a third or a fourth?